tug vs water level

tug

noun
  • A tugboat. 

  • A dog toy consisting of a rope, often with a knot in it. 

  • A trace, or drawing strap, of a harness. 

  • An iron hook of a hoisting tub, to which a tackle is affixed. 

  • A sudden powerful pull. 

  • An act of male masturbation. 

verb
  • To masturbate. 

  • To tow by tugboat. 

  • To pull or drag with great effort. 

  • To pull hard repeatedly. 

water level

noun
  • The waterline of a ship. 

  • Of a route that follows a riverbank or shoreline. 

  • An instrument to show the level by means of the surface of water in a trough, or in upright tubes connected by a pipe. 

  • The level of a body of water, especially when measured above a datum line. 

  • The level of the water table below ground. 

How often have the words tug and water level occurred in a corpus of books? (source: Google Ngram Viewer )